Does RAK7246 supports fine-timestamps

Hello Everyone,
I’m trying to setup geo-localization setup using 3 gateways (RAK7246 running RAK2246 with GPS). I successfully setup Network, Application Servers as well as Chirpstack OS and managed to connect my device. I also integrated my application server with LoRa Cloud “Modem & Geolocation Services”. But only thing I’m receiving are location frames with latitude and longitude, but source:“GEO_RESOLVER_RSSI”. I want geo-localization based on TDoA. Does RAK7246 supports fine-timestamp? If yes, what could be the problem?

I found out that RAK7246 is based on RAK2246 and it’s based on SX1308 which is not supporting Fine timestamp. Is there any possibility to get position based on GPS time?

For TDOA geolocation you need a very accurate time and this module does not provide this feature. Please note that RAK has new modules based on the sx1303 which does provide a fine-timestamp.

Thank you for your reply. One more question: according to Semtech SX1303 article the accuracy of TDoA is 75-150 meters is that correct, and can you get any better with any other of locating methods?

I think this really depends on the use-case, but other options could include for example RSSI (could be combined with TDoA), GNSS and / or wifi APs scanning. For the latter two, you do not require “special” gateways but your device needs to be capable of scanning wifi APs or GNSS scanning (e.g. the LR1110 module can do this).

Do you mean that my end-device eg. sensor, needs to be capable of APs or GNSS scanning? I’m planning to integrate my GW also with RAK 8213, so my gateway will have GNSS but is that enough to find end-device?

You can do geolocation at two sides:

  1. The gateway, in which case for TDoA your gateway needs to support the fine-timestamp (either a v2 gateway like the Kerlink iBTS or a sx1303 based gateway with GNSS module)

  2. The device, in which case it uses GNSS data (for which you need a GNSS module), its scans nearby Wi-Fi access-points (for which you need to have a module capable of scanning Wi-Fi APs), …

If you are looking at 2), then yes, each device needs to be capable of doing so :slight_smile:


Thank you for your reply, now I get it, how it needs to be done.